It is commonly asserted that with excess plant capacity, expansive policy stimulates output and lowers unemployment without substantially boosting inflation, while at full capacity most of the impact is on inflation. This assertion is critically examined. First, two common definitions of capacity--engineering and economic—are examined and found to be nebulous. The concepts of supply and demand are older, but better. Full capacity is reinterpreted as points where the supply curve is steep and excess capacity as points where it is fairly flat. Then the "Keynesian" model in which stimulative policy shifts only the demand curve is compared to the "classical" model where stimulative policy shifts both demand and supply curves. For the former model the assertion on capacity utilization is correct, while in the latter it is not. Empirical tests are performed to determine whether measured capacity utilization is useful for predicting inflation. The tests are ambiguous, but certainly do not strongly favor capacity utilization.

An overlapping generations model is developed that contains labor markets in which adverse selection problems arise. As a response to these problems, quantity rationing of labor occurs. In addition, the model is capable of generating (a) random employment and prices despite the absence of underlying uncertainty in equilibrium; (b) a statistical (nondegenerate) Phillips curve; (c) procyclical movements in productivity; (d) correlations between aggregate demand and unemployment (and output); (e) an absence of correlation between unemployment (employment) and real wages. In addition, the Phillips curve obtained typically has the "correct" slope. Finally, the model reconciles the theoretical importance and observed unimportance of intertemporal substitution effects, and explains why price level stability may be a poor policy objective.

A model of a labor market is developed in which agents possess private information about their marginal products. As a result, involuntary unemployment may arise as a consequence of attempts by firms to create appropriate self-selection incentives. Moreover, employment lotteries may arise for the same reason despite the fact that, in equilibrium, there is no uncertainty in the model. When employment is random, this is both privately and socially desirable. Finally, it is shown that the unemployment that arises is consistent with (a) pro-cyclical aggregate real wages and productivity, (b) employment that fluctuates (at individual and aggregate levels) much more than real wages.